Silver is the best. Did not care for the gold, looks a bit feminine to me!
Gunmental looks great but it shows scratches almost as bad as black and something about the speaker grilles made them appear to be stuck on decals.
Silver, OTOH, looks perfect. Same finish as a Macbook Pro!
And being the underlying metal is aluminum, scratches, even deep ones, won't stick out like a sore thumb.
Personally I like the appearance of black the best as was my M7 BUT you have to be super duper careful because scratches, even smaller ones, are GLARINGLY obvious. If you're even mildly OCD they will haunt you like a small, hard object in your sock poking at your foot with every step...